Force Field Benchmark of the TraPPE_UA for Polar Liquids: Density, Heat of Vaporization, Dielectric Constant, Surface Tension, Volumetric Expansion Coefficient, and Isothermal Compressibility

Abstract

The transferable potential for a phase equilibria force field in its united-atom version, TraPPE_UA, is evaluated for 41 polar liquids that include alcohols, thiols, ethers, sulfides, aldehydes, ketones, and esters to determine its ability to reproduce experimental properties that were not included in the parametrization procedure. The intermolecular force field parameters for pure components were fit to reproduce experimental boiling temperature, vapor-liquid coexisting densities, and critical point (temperature, density, and pressure) using Monte Carlo simulations in different ensembles. The properties calculated in this work are liquid density, heat of vaporization, dielectric constant, surface tension, volumetric expansion coefficient, and isothermal compressibility. Molecular dynamics simulations were performed in the gas and liquid phases, and also at the liquid-vapor interface. We found that relative error between calculated and experimental data is 1.2% for density, 6% for heat of vaporization, and 6.2% for surface tension, in good agreement with the experimental data. The dielectric constant is systematically underestimated, and the relative error is 37%. Evaluating the performance of the force field to reproduce the volumetric expansion coefficient and isothermal compressibility requires more experimental data.

Molecular simulation study of dielectric constants of pure fluids and mixtures

“…Another likely reason for the underestimation of the dielectric constant is the neglect of polarizability, which is common to most molecular models available to date. This hypothesis is supported by the fact that several transferable force fields also underestimate the dielectric constant [21][22][23].…”

“…Caleman et al [21] presented an evaluation of the OPLS/AA and GAFF force fields and found that most of the models underestimate the dielectric constant. Núñez-Rojas et al [22] carried out a similar study on the TraPPE/UA force field and also found that the dielectric constant is typically underestimated, with an average deviation of about 37%. Zangi [23] investigated the OPLS/AA force field for alcohols, and found an average underestimation of the dielectric constant of about 33%.…”

Parametrization with Explicit Water of Solvents Used in Lithium-Ion Batteries: Cyclic Carbonates and Linear Ethers

“…To determine the performance of nonpolarizable force fields in reproducing properties apart from those used as the target in the parameterization procedure, Caleman et al in 2011 performed a benchmark to calculate eight properties for 146 organic liquids and found out that the dielectric constant was systematically below the experimental value for all the force fields . A similar benchmark was carried out for 41 polar liquids using the TraPPE-UA force field, and also, it was found that the dielectric constant was systematically below the experimental data . Recently, the solubility of alcohols, ethers, sulfides, ketones, esters, and thiols dissolved in water was determined for 12 molecules using the TraPPE-UA force field.…”

Quantitative predictions from molecular simulations using explicit or implicit interactions

“…The CGenFF 66 produced the most accurate results for these properties. Efforts following those studies included refinement of alcohol compounds in the OPLS/AA force field, 73 using a fragment-based approach to improve liquid properties of saturated hydrocarbons, 74 parameterization of charges in OPLS/AA for 10 polar liquids, 75 tuning of the dielectric properties of chlorinated hydrocarbons, 76 a benchmark of 41 polar liquids using the TraPPe/UA force field, 77 validation of the SMIRNOFF force field 78 and, finally, a study of the interface tension of the water/oil interface. 79 The general conclusion from these studies is that liquid densities can be reproduced within 1%-2%, and energies have an accuracy of about 5-6 kJ/mol.…”

“…Dielectric constants (Equation 7) are significantly underestimated in most force fields. 34,55,77 Fluctuation properties such as β T (Equation 8) and α P (Equation 9) are challenging to reproduce since it takes a much longer simulations time to obtain converged values than, for example, the liquid density.…”